A domain is an entity/container of all DNS-related information containing
one or more records.

record

A DNS record belongs to a particular domain and is used to specify
information about the domain. There are several types of DNS records. Each
record type contains particular information used to describe that record’s
purpose. Examples include mail exchange (MX) records, which specify the
mail server for a particular domain, and name server (NS) records, which
specify the authoritative name servers for a domain.

subdomain

Subdomains are domains within a parent domain, and subdomains cannot be
registered. Subdomains allow you to delegate domains. Subdomains can
themselves have subdomains, so third-level, fourth-level, fifth-level, and
deeper levels of nesting are possible.

pointer records

DNS usually determines an IP address associated with a domain name.
Reverse DNS is the opposite process: resolving a domain name from an IP
address. This is usually achieved with a domain name pointer.